Known in the art is a method for preparing styrene from toluene which comprises passing a mixture of toluene, air and water over bismuth oxide at a temperature within the range of from 500.degree. to 580.degree. C. to produce a mixture of dibenzyl and stilbene. The dehydrodimerization products (dibenzyl and stilbene) are subjected to a catalytic hydrocracking to ethylbenzene and benzene. Thus, in hydrocracking performed at a temperature of 450.degree. C. under a pressure of 28 atm on a catalyst containing 16% by weight of Cr.sub.2 O.sub.3 on alumosilicate, conversion of dehydrodimerization products is 26%, the yield of ethylbenzene is 31.8% by weight. The resulting ethylbenzene is subjected to dehydration to styrene.
Also known in the art is a process for producing styrene consisting in that dibenzyl resulting from dehydrodimerization of toluene is subjected to conversion directly to styrene and benzene. Thus, in the presence of a catalyst containing, percent by weight: SiO.sub.2 73; Al.sub.2 O.sub.3 --17; Fe.sub.2 O.sub.3 --1.5; MgO--4; CaO--2, at the temperature of 550.degree. C. and space velocity of 18.3 hr.sup.-1, conversion of dibenzyl is 18.7%; the yield of styrene is 22.4% by weight.
Upon dehydrodimerization of toluene there is formed a mixture of dibenzyl and stilbene, wherein the dehydrodimerization products can be subjected to conversion to styrene only after a preliminary hydrogenation of stilbene.
The prior art methods have certain disadvantages residing in a low yield of styrene and multi-stage character of the process.